The Yankees can’t keep on going like this and hope to be a playoff contender. An overreliance on their relief pitchers is not a sustainable model to keep winning baseball games let alone play in the postseason.

In a 7-6 win over the Twins last night that ironically lifted their record to 7-6, the Yankees may have won with their bats but their inability to get their pitchers deep into the game is putting undue pressure on their starting rotation. Consider the example of Thursday night where starter Phil Hughes pitched just one out into the sixth inning. Four relievers, including Mariano Rivera’s perfect ninth inning, cinched the win for the Yankees, but it is a worrisome trend for the club that they can’t get their starters to go deep into games.

The depth of the starting pitching and therefore the bullpen is a concern, which may lead to rubber arms come August and September.

Only C.C. Sabathia, with 23 innings pitched in three starts, is in the top 25 in the league in innings pitched. The Phillies, Rangers and Rays, all popular picks to make the playoffs, each have two starters among the top 25 in innings pitched, underscoring that the Yankees rotation just isn’t cutting it.

The Yankees arm race during their mediocre start to the year just isn’t cutting it and is baseball’s version of Mutually Assured Destruction (MAD). The starters can only go so far until they run into trouble or start losing their control, meaning that Girardi needs to keep calling only his bullpen earlier and earlier to salvage games. This in turn puts undue pressure on his relievers to go long into the game, night in and night out to keep things close or hold onto one of their seven wins this season.

So to win games and salvage the effort of his starting pitching, Girardi needs to lean heavily on his bullpen. In turn, he may not have a bullpen after the All-Star break if he keeps calling on them this way. Girardi is in a bind.

It’s a maddening prospect that doesn’t bode well for the rest of the season or the team’s viability to be playing baseball when the leaves begin turning colors.

With Andy Pettitte expected to return in three weeks and Michael Pineda continuing his rehab, the Yankees rotation should be getting deeper. But when Pettitte returns, it will be as part of a six-man rotation meaning that the bullpen won’t necessarily get an upgrade in talent or depth.

And with Joba Chamblerlain’s timetable for return still very much up in the air, the Yankees either need to get more quality starts from everyone else in their rotation not named Sabathia or they need to make a deal for some bullpen relief and find an innings eater.

But after all that, is it really cause for concern?

Last year en route to a 97-65 record and the AL East title, only Sabathia was a true constant on the mound, tied for fourth in the league with 237.1 innings pitched. He was far and away the biggest Yankee contributor, consistently going deep into games.

The next closest Yankee last season was A.J. Burnett, who averaged nearly an inning and a half per game less than Sabathia.

But after the miles he put on his arm last year and the fact that the Yankees rotation is getting older with the return of Pettite, the rest of Girardi’s starters need to start going further into games. If not, there may not be any arms left in the bullpen for the playoffs – they might get used up just getting there.

Kristian R. Dyer covers sports for Metro New York and contributes to Yahoo!Sports. Follow him on Twitter @KristianRDyer